I support the steep learning curve idea; I think GavJ's argument is based on mislabeled axes. The traditional graph uses "time passed" as the independent X axis, and "skill required", not "total skill gained" as the dependent Y axis. Therefore, a steeply rising curve shows that a great quantity of skill is needed in a very short amount of time.
1) No, the traditional graph does not use that. It uses skill gained. This is an actual psychology term used for legit research, and that's the meaning of the curve
http://en.wikipedia.org/wiki/Learning_curvealthough if you insist I could actually go take the time to look up some journal articles. I've read them before, but it was ages ago in undergrad. They use the same thing the wiki article does. It's learning. I.e. cumulative learning / understanding gained so far, as in my original graph in the OP.
Note, especially, the line "The familiar expression "a steep learning curve" is intended to mean that the activity is difficult to learn, although a learning curve with a steep start actually represents rapid progress."
2) "Skill required" is super vague, and could mean various mathematically distinct things:
Do you mean "Skill required to master the game?" That would be a flat line, at all time points, as it is a fixed amount as a goal, and doesn't change as you learn.
Do you mean "Skill required to survive until the next tick?" That would be a crazy up and down constantly zig zag mess of a useless graph that you couldn't interpret anything from. Because some ticks, you don't need to do anything to survive til the next tick. Other ones, you may need to do a dozen crazy things. Then nothing again...
Or do you mean something else? Please operationalize this much more precisely. I am unable to interpret it in a way that would actually lead to the curve shape anything like what you're describing.
Wait, no, now I remember. It's not about what you learn, it's about the difficulty of learning it.
Steep learning curve: It's easy for a bit, then it's extremely hard.
Shallow learning curve: It is easy to learn the whole time.
The difficulty of learning "it." What is "it?" The next quantum bit of knowledge? Okay, that could be graphed, but like the above, seems very unlikely to be a smooth curve. As you learn, some things that come up are super super easy. Like, I dunno, setting up a hospital. It's just a zone and then you hit "H" But you don't do that until pretty far into a fort, so it's midway along the X axis. With things more difficult than it on both sides.
In other words, this would also be a crazy mess of a zig zag line with no fluid continuity to it. Not a nice smooth steep slope. I don't even see any reason to believe in dwarf fortress that the moving AVERAGE of this would be a steep slope, or even a slope at all. What makes you think stuff in DF gets harder to understand as you go? That was not my experience at all...